Metal-to-ceramic leadthrough

ABSTRACT

A metal-to-ceramic leadthrough with the use of glass-like material and an aperture having a narrow portion which changes in a step-wise manner into a widened portion, the gap between the conductor and the wall of the narrow portion being filled entirely with glass-like material and the bottom of the wide portion of the aperture being covered with a thin layer of glasslike material which forms a meniscus against the conductor and the inner wall of the wide portion of the aperture.

United States-Patent 11 17 Me'rz etal.

[5 METAL-TO-CERAMIC LEADTHROUGH, [75] lnventors: Josef Me rz, Hamburg, Germany;

- Johannes Van Esdo'nk; Joannes Francis cus Maria Janssen, both of Emmasingel, Eindhoven,

, Netherlands v [73] Assignee: U.S. Philips Corporation, New York, NY.

[22] Filed: Nov. 22, 1972 21 Appl. No.2 308,685

[30] v Foreign Application Priority Data 5 v Dec. 1, 1971 Germany, 215 953 {52 U.S. c1. 403/29 [51] Int. Cl F16!) 11/00, C03C 27/02 [58] Field of Search 403/28, 29, 179, 270, 27 1; 52/759 65/36, v59; 29/180 NM [56] References Cited 1 UNITED STATES PATliNTS 1451" Dec. 17, 1974 3,219,753 11/1965 I Vassos 403/28 x 3,278,211 10/1966 Baas etal. 403/29 3,370,874' 2/1968- Scherer et al I 403 /28 3,385,618 5/1968 ,Hargis 403/271 3,436,109 4/1969 Loose 52/759 3,545,950 12/1970 Earl 65/59 3,600,017 8/1971 Scherer- 52/759 Primary Examiner werner H. Schroeder Attorney, Agent, or Firm-Frank R. Trifari [57] ABSTRACT U A metal-to-ceramic leadthrough with the use of glasslike material and an aperture having a narrow portion 1 which changes in a stepwise manner into a widened portion, the gap between the conductor and the wall of the narrow portion being filled entirely-with glass-.

like material and the bottom of the wide portion of the aperture being covered with a thin layer of glass-like material which formsa meniscus against'the conductor and the inner wall of the wide portion of the aperture.

2 Claims, 1 Drawing Figure- The glass-like material preferably composition: r

' 3,545,950. ln this patent the wide portion of the aperture is filled by means of a member consisting of a glass-like materialwhich has a cavity on its upper side.

By accurately controlled heating it.is achieved that the glasslike material softens in such manner as to adhere to the conductor andto'the inner wall-.ofthe widened portion of the'ap'erture but without amenisc us being formed against themetal surface and without the gap between the conductor and the inner wallof the narrow portion of the aperture being filled. The glass-like material may thus not becomethin-liquid.

It has been found, however, that as-a result of such a large accumulation of glass-like material in the wide portionof the'aperture, cracks can occur in the glasslike material during cooling after softening said materialQThis is the case also if a conductor is secured in a wall having a thickness of more than 2 mm by means of a glass-like material while using a narrow aperture having a constant diameter. 1 7

It has been found that the said difficulty can be avoided entirely in a metal-to-ceramic leadthroughin which a metalconductor is. secured inan aperture of a ceramic wall having a thickness of more than 2 mm by means of glass-like material, which aperture consists of a narrow portion which changes step-wise into a wider portion, it, according totheinvention, the quantity 'of glass-like material is chosenand provided in such manher and is heated to such a high temperature that the 37 percent by weight MnO, 50 percent by weight SiOz 13 percent by weight M 0 7 3 Melting is carried out at l,300C for 10 minutes. The conductor may consist of molybdenum sary for certainv applications.

ln metal-to-ceramic joints it is known to use apertures which are widened in a step-wise manner, forexample, from the US. Pat No. 3,385,6l8 in which a metal solder-is used which forms a meniscus against the conductor and a thin layer on the bottom of the wide portion. in this case, however, the gap between the conductor'and the inner wallof the narrow portion of the aperture must remain free from soldering material so as to be able to compensate for the differencein coefficients in thermal expansion between metal and eeramic. The widened portion of the aperture serves to be able to metallize the whole surface and to be able to remove said metal layer afterwards from the upper surface, the metal layer on the bottom of the widened portion of the aperture being maintained which is necessary to cause the metal solder to flow.

in the US. Pat. No. 2,731,578 the widened aperture is provided so as to obtain an insulation path between the metallized surface of the ceramic part and the lead through conductor.- In British Pat. No. 522,217 the widened portion of the'aperture is provided so as to be able to connect any contact members tothe leadthrough glass-like material has entirely filled'the gap between the'conductor and the inner-wall of thenarrow portion of the aperture, but has formed a' comparatively thin layeron the bottom-of the wide portion of the aperture, said thin layer forming ameni'scus both against the conductor and against the'inner wall of the wide portion of the aperture. The length of the narrow portion of the aperture may preferably be equalto that of the wide portion but must at least be so large that the desired seal is obtained but may atmost not exceed approxi-' mately 2 mm so as to avoid'cracking of the-glass-like layer during cooling after melting thereof or afterwards during operation. Since the thin glass-like layer forms a meniscus on the bottom of the wide portion of theaperture. against the metal surfaceand against the inner wall of said portion of the aperture, it has-been found that in this case also no cracks are formed while asufficient mechanical rigidity is obtained. The thickness of the glass-like layer on the bottom of the wide portion of the aperture is from lOO to 1,000 s, which layer I forms a meniscustowards the edge of the conductor and towards the inner wall of the aperture. The diameter of thewide portion of the aperture is preferably three to four times as large as the diameter. of the narrow portion 7 g has thefollowing conductor. When using metallic soldering material,

however, the circumstances are quite differentfrom.

those occuring when a glass-like material is used.' 7 The invention will be described in greater detail with reference to the accompanying drawing, the FIGURE of which shows a metal-to-ceramic leadthrough ac-- cording to the invention. i

Reference numeral l in the FIGURE denotes a ceramic wall of 4 mm thicknessthrough which a molybdenum conductor 2:having'a diameter of 1.5 mm is passed. The aperture in" the wall 1 has a narrow portion 3 having a diameter of l'.6 mm and a widened portion 4 having adiameter of 6 mm. The gap between the'conductor 2 and the inner wall of the-portion 3 of the aperture is entirely filled with glass-like material 5 of the above-described composition. the bottom of the por-' tion 4 ofthe aperture is covered with a layer "6' of the glass-like-material 5. The thickness .of the layer 6' may be from 100 to l,000 t. The layer 6 forms a meniscus 7 both on the metalsurface of the leadthrough conductor 2 and on the inner wall 8 of the portion 4 of the aperture. After placing the conductor 2 in the aperture, the suspension is provided on the bottom of the wide v portion '4. Melting occurs in a reducing atmosphere at a temperature of l, 300C for 10 minutes, the layer 6 with the meniscus7 being formed and the gap between the conductor 2 and the inner wall of the aperture 3' being filled. Since the way of heating is not critical, a ceramic wall having a large number of leadthrough conductors may be heated in a furnace in which all the conduetorsare sealed simultaneously.

Metal-to ceramic' leadthroughs according to the invention have proved particularly suitable; for use in .digital light deflection systems whichare provided in a eeramic vessel, said vessel being filled with-liquid and the leadthrough conductors consisting'of molybdenum. What'is claimed is: v

l. A metal-to-ceramic leadthrough, comprising: a ceramic wall portion that has athickness of more than 2 which is neces-,

entirely filling the gap between the conductor and the inner wall of the narrow portion of the aperture, said body forming a relatively thin layer on the bottom of the wide portion of the aperture and said thin layer forming a meniscus both against the conductor and 3 against the inner wall of the wide portion of the aperture, said conductor consisting of a material having a coefficient of thermal expansion which is lower than that of the ceramic portion. I

2. A metal-to-ceramic leadthrough as in claim 1, wherein said conductor material consists essentially of molybdenum.

CERTIFICATE? OF- CORRECTION 8 1 Dated December 17, 1974 7 It is certifiz lg'd that rror appears in the aboveddjehtified pat'nc and that said Letters Pate nt are hereby corrected as shown below:

[on the 7 title a e; Section [30] change "215931" sigheqf and sealed this 18th day of February 1975.;

(sEALf \Attest:

c. MARSHALL DANN C. Comissioner of; Patents Arresting Officer I and Trademarks- ,32 3 UNETED STATES RWENT @FFKQE fiERTWICATE OF QGRRECTION Pai e: No. 3,854,827 Dated December 17, 1974 ln tofls) JOSEF MERZ ET AL It is certified that error appears in the ahc ve-icintifiez3 and that said Letters Patent are hereby ccar'recfced as shown below:

On the titlepage, Section [30] change "215931" to -P.2l593l 3.

Signed and sealed this 18th day of February 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks 

1. A metal-to-ceramic leadthrough, comprising: a ceramic wall portion that has a thickness of more than 2 mm and that includes an aperture comprising a narrow portion which changes in a stepwise manner into a wider portion, said narrow portion having a length that is at most about 2 mm; a metal conductor disposed in said aperture and spaced by a gap from the aperture wall; and a body of glass-like material disposed at and entirely filling the gap between the conductor and the inner wall of the narrow portion of the aperture, said body forming a relatively thin layer on the bottom of the wide portion of the aperture and said thin layer forming a meniscus both against the conductor and against the inner wall of the wide portion of the aperture, said conductor consisting of a material having a coefficient of thermal expansion which is lower than that of the ceramic portion.
 2. A metal-to-ceramic leadthrough as in claim 1, wherein said conductor material consists essentially of molybdenum. 